package LeetCode_Section;
//环形链表
//https://leetcode.cn/problems/linked-list-cycle/description/

public class AnnularLinked {
class ListNode {
    int val;
    ListNode next;
    ListNode(int x) {
      val = x;
      next = null;
    }
}

    public class Solution {
        public boolean hasCycle(ListNode head) {
            ListNode fast = head;
            ListNode slow = head;
            if (head == null) {
                return false;
            }
            if (head.next == null) {
                return false;
            }

            while (fast != null && fast.next != null) {
                fast = fast.next.next;
                slow = slow.next;
                if (fast == slow) {
                    return true;
                }
            }

            return false;
        }
    }
}
